Josh Duhamel was recently interviewed by the Detroit Free Press. In the article, they discuss his work and non-work related visits to Detroit, including filming "Transformers". Among his comments on Transformers, Duhamel says:
"When he's not costarring with robots that turn into autos and other vehicles, Duhamel drives a truck -- "that's why Ironhide is my favorite Transformer," he says about a truck."
Among other topics he discusses are the stunt work he had to do for the films. You can read the entire article here.